This present invention relates to a new development of internal combustion engines (i.e. where combustion takes place in the working fluid) of positive displacement type, which consists of the novel combination of elements, as described in the abstract and in the detailed description of the invention, having the following objects and outstanding performance that will become more apparent as this description proceeds:
(a) Availability of means to adjust, within a suitable range, the air pressure for filling the combustion chambers. This can be accomplished in the engine of the invention by setting the maximum and minimum clearance limits of the compressor cylinders respectively to the minimum and maximum volume limits of the combustion chambers.
(b) Capability to maintain constant the air pressure for filling the combustion chambers at the value previously selected and adjusted to obtain optimum thermal efficiency of the engine in accordance with the characteristics of the fuel used. This is achieved in the engine of the invention by increasing or decreasing automatically the clearance of the compressor cylinders in accordance with pressure signals from the header that conveys compressed air to the combustion chambers.
(c) Availability of means to adjust, within a suitable range, the air/fuel ratio. This can be accomplished in the engine of the invention by setting the maximum and minimum volume limits of the combustion chambers respectively to the maximum and minimum charge of fuel injected.
(d) Capability to maintain constant, at any load of the engine, the air/fuel ratio at the value previously selected and adjusted to obtain optimum thermal efficiency of the engine.
The selection of such value shall be done in accordance with the characteristics of the fuel used. This is achieved in the engine of the invention by increasing or decreasing automatically the volume of the combustion chambers in proportion to the charge of fuel being injected (i.e. according to the position of the accelerator pedal or other suitable signal from the fuel injection system) and maintaining at the same time constant the air pressure used for filling and pressurizing the combustion chambers prior to fuel injection.
In current compression-ignition diesel engines, the air/fuel ratio changes depending on the load demand; when the engine operates at low load an excess of air unneeded for combustion is drawn into the cylinder and therefore some work is wasted to compress that excess of air.
In current gasoline engines using a carburator with a throttling valve, a pressure drop takes place across such valve when the engine operates at low load, with the throttling valve partially closed, and therefore the final pressure obtained in the cylinder before spark ignition is lower than the pressure obtained when the engine operates at high load, with the throttling valve fully open.
(e) Availability of long periods of time within the operating cycle to achieve the fuel injection and combustion inside the combustion chambers with closed valves, so that no back pressure is passed to the power cylinders during exhaust strokes and no back pressure is passed to the compressor discharge header.
In the preferred embodiment of the invention having two combustion chambers associated with (or serving) each power cylinder, the total time available for fuel injection and combustion is equal to the time in which the power piston makes three strokes. Obviously, the fuel injection may be arranged to start at any time within such total period of time avaialble. The selection of the optimum time to start fuel injection will depend on the characteristics of the fuel used and/or the speed of rotation of the engine.
The long period of time available for fuel injection and combustion makes possible the use of heavier fuels (i.e. fuels that need more time to obtain complete combustion). Such long period of time within the operating cycle makes possible a higher speed of rotation of the engine as compared to other engines having a shorter period of time for combustion. The higher speed of rotation will permit a reduction in the size (or volumetric displacement) of the engine for the same given power output.
(f) Availability of means to obtain a regenerative braking. The compressor is used to slow down the engine and vehicle driven by the engine. During this braking mode the accumulator is used to store the compressed air delivered by the compressor for subsequent use when needed.
This is accomplished in the engine of the invention by increasing the capacity (or output) of the compressor and at the same time decreasing to a minimum the volume of the combustion chambers, so as to obtain an excess of compressed air not used for combustion that is passed to the accumulator. During this braking operation the power input required to drive the compressor is higher than the power output obtained from the power cylinders and therefore a negative power is obtained to slow down the engine and vehicle.
The compressed air stored in the accumulator can be used during periods of power demand (acceleration) to feed the combustion chambers with the necessary air, saving compression work in the power cycle and therefore obtaining more power output from the engine than in the normal operating mode in which the compressor has to do work.
The compressed air stored in the accumulator can also be used to feed the compressor, which will increase the clearance of its cylinders, saving compression work and obtaining more power output from the engine.
Above operations of super power output are accomplished by the engine of the invention by means of a valve that closes the intake header of the compressor and/or by increasing the clearance of the compressor cylinders as much as required to obtain proper air pressure in the discharge header which feeds the combustion chambers.
(g) Possibility to use the engine as a compressor driven by the power cylinders.
(h) Availability of compressed air stored in the accumulator to start the engine or for other use if required.